All electromagnetic radiation consists of oscillating electric and magnetic fields and the frequency, which is the number of times per second at which the wave oscillates, determines their properties and the use that can be made of them. Frequencies are measured in hertz or Hz, where 1 Hz is one oscillation per second, 1 kHz a thousand, 1 MHz is a million, and GHz, is a thousand million. Frequencies between 30 KHz and 300 GHz are widely used for telecommunications, including broadcast radio and television, and comprise the radio frequency band.
Cellular mobile services operate at frequencies authorised by governments and typically operate within the frequency ranges 872-960 MHz, 1710-1875 MHz and 1920-2170 MHz. These frequencies are within the microwave frequency band which encompasses the range between 300 MHz and 300 GHz. Wi-Fi Communications operate at frequencies authorised by governments and typically operate between frequency bands 2.4 GHz and 5 GHz ISM. Other applications within this range include radar, telecommunication links, satellite communications, weather observation and medical diathermy. This invention is particularly useful with devices that operate on frequencies used for cellular telephones.
A radio frequency wave used to carry information in radio communications is referred to as a carrier wave. The radio frequency carrier wave of any system is produced by the transmitter as a sine wave, or other regular waveform. A carrier wave conveys no information if its properties do not vary in time. If the carrier wave is to convey any information, for instance, speech, music or digitized data, this information has to be added to it in some way. The process of varying one or more properties of a carrier signal with respect to the information that it is to carry is known as modulation. Properties of the carrier wave that may be varied through modulation include for instance, amplitude, frequency, phase or any combination of these. For example, for AM (amplitude modulation) transmission, the electrical signal from a microphone produced by speech or music is used to vary the amplitude of the carrier wave, so that at any instant the size or amplitude of the RF carrier wave is made proportional to the size of the electrical modulating signal. In FM (frequency modulation), the instantaneous frequency of the carrier deviates from the carrier frequency by an amount dependent on the strength of the modulating signal. Phase modulation (PM) is a form of modulation that represents information as variations in the instantaneous phase of a carrier wave. FM and PM are very commonly used for current day radio communications.
A mobile phone (cell phone) sends and receives information (voice messages, text messages, emails, fax, computer data, downloads information etc) by radio communication. Radio frequency signals are transmitted from the phone to the nearest base station and incoming signals (carrying the information from the source to which the phone user is listening) are sent from the base station to the phone at a slightly different frequency. Base stations link mobile phones to the rest of the mobile and fixed phone network. Once the signal reaches a base station it can be transmitted to the main telephone network, usually by an optical fiber network.
Each base station provides radio coverage to a geographical area known as a cell. Base stations (BS) are connected to one another by a mobile services switching centre (MSC), which tracks calls and transfers them as the caller moves from one cell to the next. An ideal network may be envisaged as consisting of a mesh of hexagonal cells, each with a base station at its centre. The cells overlap at the edges to ensure the mobile phone users always remain within range of the base station. Without sufficient base stations in the right locations, mobile phones will not work. If a person with a mobile phone starts to move out of one cell into another, the controlling network hands over communications to the adjacent base station.
There are conflicting views as to the effects of electric fields, magnetic fields and electromagnetic fields on living systems. However there is considerable evidence showing that certain fields are able to trigger a range of biological effects in various biological systems and that these effects may be damaging to living systems including humans. There are now also a growing number of studies linking mobile phone use to serious health issues such as brain tumours and infertility. It may also be that the detrimental effects are long term and their full impact has not yet been realised. WO 02/00468 recognises that the reaction may be harmful and provides a system that detects radiation and issues a warning if a level of radiation is exceeded. It does not however determine if the radiation is potentially harmful and does not take any remedial action to rectify the situation.
There has been a dramatic increase around the world in the use of electrically operated devices particularly battery powered hand held mobile telephones. All such devices have associated with them electromagnetic field emissions which, to varying degrees, have the potential to affect human health. Of particular interest are devices that transmit radio frequency (RF) signals and are used in close proximity to the human body particularly the head, for instance hand held cellular phones and other personal communication devices. At issue is the possibility that the safety standards under which these devices are manufactured, which establish RF exposure limits to the users of these devices, may not adequately account for effects below the thermal threshold, that is, at exposure levels well below levels that can produce measureable heating and can be attributed to direct energy transfer. The potential for such low level effects is supported by substantial evidence from epidemiologic studies and laboratory research which suggests that any measures that could reduce and/or minimize the effects of such exposure would be beneficial to the users of these devices. Laboratory research also suggests that the severity of impact from RF exposure at non-thermal levels is dependent on the modulation characteristics of the RF signal, in particular amplitude variations in the low frequency envelope. Signals that display a greater degree of regularity have been shown to have greater biological impact.
Modern mobile devices include a wide range of services which employ complex communication schemes. In the operation of such devices, the modulation characteristics of transmitted RF signals can vary substantially depending on the type of information that is being transmitted, for instance, voice or data. Accordingly, the extent of biological effects can also vary. It is therefore desirable that a remedial system be capable of assessing the nature of the modulation to determine the potential extent of biological impact. Furthermore, such a remedial system should be compact and adaptable for use with different telephone handsets and different battery systems. Additionally it is desirable that the remedial system operates effectively, is only used when required as determined by the emitted radiation and hence consumes little power from the battery to preserve battery life.
U.S. Pat. No. 5,544,665 is concerned with the protection of living systems from the harmful effects of electromagnetic fields and states that certain fields have an effect on the enzyme ornithine decarboxylase. The patent states that the potentially damaging effect can be reduced or eliminated if the detrimental electromagnetic field is altered either by switching the field on and off or superimposing an electromagnetic noise field upon it. The patent further states that the effect can only be reduced if such alteration causes relevant characteristic properties of the field to change in time at intervals of less than 5 seconds and preferably at intervals from 0.1 to 1 second. The characteristic properties that can be changed are said to be frequency, phase, direction, waveform or amplitude. Similar effects are discussed in Bioelectromagnetics 14 395-403 (1993) and Bioelectromagnetics 18 388-395 (1997).
U.S. Pat. No. 5,544,665 dates from 1991 and describes various applications of the bio-protection scheme including applications to cellular telephones of the type available at that time which were bulky and used only for voice transmission. The EMX Corporation has promoted batteries for such cellular telephones that make use of the technology described in U.S. Pat. No. 5,544,665. When used with a cellular phone, these batteries are said to produce an electromagnetic noise field that is superimposed over the local RF field generated by the operation of the telephone for voice transmission thereby causing the total field to be irregular and thus not likely to cause biological effects. The noise was generated by a coil forming part of the battery pack. Activation of the noise was accomplished by monitoring the flow of electric current from the battery to the phone and using this as an indirect means to determine when the phone was transmitting RF fields that were likely to produce biological effects. This activation technique worked reasonably well with older phones but proved to be unreliable with newer phones that now have many more applications that demand power from the battery but do not produce RF fields. Use of such applications could cause false triggering of the noise and potentially unnecessary and unacceptable reduction in battery life.
GB Patent Application 2482421 A provides a system that determines when RF emissions are being emitted from a personal communication device such as a mobile telephone. According to GB 2482421 when an emission is detected the system outputs a low frequency modulated RF confusion field from an RF transmitter located within the personal communication device, as opposed to a low frequency magnetic field. The determination is made based on information provided by the RF transmission module and not by either the detection of the presence of the signal, or analysis of the signal to determine whether the signal is likely to cause biological effects. This may be costly and to generate the confusion signal is power consuming.
In WO 2012/041514 we describe technology that addresses these issues and provides a process, an apparatus and systems for the reduction or elimination of the potentially harmful effect on humans or animal life caused by exposure to electromagnetic fields produced by devices that operate by transmitting RF signals. The technology comprises a device provided with means to reduce or eliminate the potentially harmful effect of the RF signals and further provided with a means to sense and analyse RF fields and assess their ability to produce biological effects, and which activates the means to reduce or eliminate the potentially harmful effect of the measured RF signals on humans or animal life based on the outcome of that assessment.
The techniques described in WO 2012/041514 prefer to employ the combination of a passive radio frequency detector to monitor the local RF field which wakes up an active radio frequency detector when a potentially harmful bio-effective field is detected. The passive detector would activate (Power on) the remedial device to initiate analysis of a radio frequency signal received by the antenna by means of a remedial control module. This system does not however provide adequate power management for both the required term operation of the device and the detection and analysis of the potentially harmful signal and the generation of the remedial signal.
We have found that particularly when used with modern day battery powered portable telephone handsets with so many functions the constant powering of such an active circuit by the battery can create an undesirable drain on the battery. Accordingly the present invention provides a design which minimizes power consumption while allowing monitoring of the RF field and providing any remediation that may be required.